1. Field of the Invention
The present invention relates to a steering system.
2. Description of the Related Art
In a telescopic adjustment type steering system that adjusts the position of a steering wheel, which is a steering member, in an axial direction of a steering shaft, an inner shaft and an outer shaft that constitute the steering shaft are fitted to each other so as to be non-rotatable relative to each other and slidable relative to each other in the axial direction, and both the shafts are caused to slide relative to each other in the axial direction so as to perform telescopic adjustment. For example in Japanese Patent Application Publication No. 2006-151011 (JP 2006-151011 A), in a steering shaft, a rolling element is rollably retained by an annular bush inserted into an inner periphery of one end (open end) of an outer shaft, and the rolling element is pressed against an outer periphery of an inner shaft by the elastic force of the bush, in order to perform the telescopic adjustment smoothly.
Additionally, for example, in International Publication No. WO03/031250A1 in a steering shaft, a rolling element is interposed between an end portion of an inner shaft and an inner periphery of an outer shaft.
In the telescopic adjustment type steering system, a jacket, which supports the steering shaft so that the steering shaft is rotatable, is constituted by an outer tube and an inner tube that are fitted to each other so as to be slidable relative to each other in the axial direction. At the time of a secondary collision in which a driver collides with the steering wheel due to a collision (primary collision) of a vehicle, both the tubes slide relative to each other in the axial direction so as to absorb shock energy.
However, since the steering wheel tends to be pushed upward at the time of the secondary collision, a twist is apt to be caused between the outer tube and the inner tube. If the twist is caused, the sliding resistance between both the tubes may become large and both the tubes may not be able to smoothly slide relative to each other when shock is absorbed. In the case where the length of fit between both the tubes is set to be long in order to reduce the twist between both the tubes when shock is absorbed, it is difficult to reduce the size of the steering system in the axial direction while securing a required shock-absorbing stroke.